This invention relates to electron radiography and in particular, to a new and improved method and apparatus for handling the imaging gas in the imaging chamber of an electron radiographic system.
In a typical electron radiographic system, an imaging gas of high atomic number such as xenon or krypton, is maintained under several atmospheres pressure between electrodes in an imaging chamber. The imaging chamber is opened after each exposure to remove the exposed receptor sheet and insert a new receptor sheet. The gas which was in the imaging chamber at the time of opening is lost, and after closing, the imaging chamber is filled with atmospheric air at ambient pressure.
The imaging gas is expensive and it is desirable to recover as much of it as possible. Also, the imaging gas which is recovered should be kept pure for subsequent reuse. One gas handling system for an electron radiography imaging chamber is shown in U.S. Pat. No. 3,828,191. In this system, the air is purged from the imaging chamber after closing utilizing carbon dioxide. The carbon dioxide is flushed out by the imaging gas and the imaging chamber is ready for the exposure. After exposure the imaging gas is flushed out with carbon dioxide and this gas mixture is treated to remove the carbon dioxide, typically by use of a lime reaction. Water from this reaction is then absorbed by another chemical. This system requires three expendables, the carbon dioxide, the lime and the water absorbing material.
It is an object of the present invention to provide a new and improved closed cycle gas handling method and apparatus which does not utilize expendables and which does not require servicing for replacement of expendables. Of course, it should be realised that there always may be some loss of gases due to leaks and to errors in operation.